diff --git a/specification.md b/specification.md
index 4459c43..959eac3 100644
--- a/specification.md
+++ b/specification.md
@@ -631,7 +631,7 @@ An HTML coverage report can be obtained following *simple* instructions inside t
 ### Dependencies
 
 The *prerequisites* section of the README enumerates the dependencies.
-The implementation should not have any dependencies apart from the C (or C++) standard library and a unit testing framework.
+The implementation should not have any dependencies apart from the C (or C++) standard library, system libraries (POSIX), and a testing framework.
 
 The unit testing framework is *vendored* and automatically used by the build system.
 See the getting started code-base for an example.